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Population size. In population genetics and population ecology, population size (usually denoted N) is a countable quantity representing the number of individual organisms in a population. Population size is directly associated with amount of genetic drift, and is the underlying cause of effects like population bottlenecks and the founder ...
List of countries by population (United Nations) This is a list of countries and other inhabited territories of the world by total population, based on estimates published by the United Nations in the 2024 revision of World Population Prospects. It presents population estimates from 1950 to the present. [2]
The Demography of the World Population from 1950 to 2100. Data source: United Nations — World Population Prospects 2017. Demography (from Ancient Greek δῆμος (dêmos) 'people, society' and -γραφία (-graphía) 'writing, drawing, description') [1] is the statistical study of human populations: their size, composition (e.g., ethnic group, age), and how they change through the ...
The effective population size (N e) is the size of an idealised population that would experience the same rate of genetic drift as the real population, whereby the latter, due mainly to the limited proportion of breeding individuals, has a normally larger census population size N. Idealised populations are based on unrealistic but convenient ...
A statistical population can be a group of existing objects (e.g. the set of all stars within the Milky Way galaxy) or a hypothetical and potentially infinite group of objects conceived as a generalization from experience (e.g. the set of all possible hands in a game of poker). [2] A common aim of statistical analysis is to produce information ...
Human population planning is the practice of managing the growth rate of a human population. The practice, traditionally referred to as population control, had historically been implemented mainly with the goal of increasing population growth, though from the 1950s to the 1980s, concerns about overpopulation and its effects on poverty, the ...
The half-life of a population is the time taken for the population to decline to half its size. We can calculate the half-life of a geometric population using the equation: N t = λ t N 0 by exploiting our knowledge of the fact that the population (N) is half its size (0.5N) after a half-life. [20]
The Ne of a population is closest in size to the generation that had the smallest Ne. This is because alleles lost in generations of low populations are not regained when the population size increases. For example, the Northern Elephant Seal was reduced to 20-30 individuals, but now there are 100,000 due to conservation efforts.